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In this report a new method to design reinforced concrete floor slabs which terminate at edge beams is presented. The design procedure uses the Modified Yield Line Theory of Kemp and Wilhelm to account for the influence of torsional stiffness of edge beams on the load carrying capacity of slab and also to provide the economic reinforcement. Serviceability requirement of the structure is satisfied by using the "exact" elastic solution and the experimental and theoretical work of this investigation. The necessary theoretical derivations of the "exact" elastic solution of square panels, design formulas to proportion the spandrels of both rectangular and square panels, ultimate equilibrium equation of the Modified Yield Line Theory, formulas for factor of safety against flexural cracking and combined effect of torsion and shear interaction on edge beams, etc. are first time successfully worked out and incorporated in this report. Also, two mathematical inequalities are developed which represent necessary conditions for the formation of torsional hinges in edge beams. Reasonableness of these inequalities is checked by the test data and' observed behavior of the structure. Three micro-concrete models of rectangular and square slabs of aspect ratios 1:1, 1:1,5 and 1:2 are fabricated and tested at the Concrete Research Laboratory of West Virginia University. The appropriate part of the test data is correlated with the previous 197 prototype test results and also with the elastic theory developed in this report, thus establishing the reliableness of these model tests. Statistical methods are used to analyze the test data. Thus, the observed behavior, well established elastic solution, existing test data, statistical methods, sound concepts of the Modified Yield Line Theory, etc. contribute to the development of the simple and direct procedure to design reinforced concrete rectangular and square slabs which terminate at edge beams.